The present invention relates to grille systems having improved strength and rigidity. The grille systems of the present invention are particularly useful as security grilles and load bearing grilles.
Grille systems generally comprise a lattice, grating or screen made from metal parts welded to one another. Grilles can be used over windows and doors of buildings to secure the building against intruders. Such security grilles are usually mounted on the brickwork, masonry or concrete of the building and although specialists can be used to fit the security grilles the majority of users prefer to be able to fit the grille themselves to save on costs.
Grille systems can also be used in a variety of other applications including the manufacture of garden furniture and decorative supports for plants together with household furniture such as shelving systems. Garden furniture, household furniture and plant supports are often large items and it is therefore advantageous to be able to buy these items in kit form for self-assembly.
British patent number 2 206 916 in the name of Alan David Pitt relates to a security grille for self-assembly. The grille is formed from a number of rods received by clamping members to form a grille of the desired size, shape and design.
The grille system of British patent number 2 206 916 has associated with it the problem of the application of a load, particularly at right angles to the rods, resulting in the rods withdrawing out of the clamping member. This is very undesirable in security grilles as it means the grille can be deformed and even dismantled by the application of appropriate force.
When used in the manufacture of garden furniture or supports for plants the problems associated with the prior art system can lead to deformation or destruction of the article if a great load is applied thereto.
The present invention aims to overcome the problem associated with the prior known grille system.
Accordingly the present invention provides a grille system comprising at least two rod arrangements and at least one clamping member to retain the rod arrangements in a predetermined spatial configuration, each rod arrangement having at least a first end portion and a second end portion wherein at least the first end portion of each rod arrangement is received by a clamping member and at least the first end portion of each rod arrangement is provided with an expanded portion to prevent the rod arrangement from being withdrawn from the clamping member.
The use of an expanded portion on the end portion of the rod arrangement to be received by the clamping member creates a stop which is held in the clamping member even when force is applied to the resulting grille system, for example at right angles thereto. The result is a grille system having improved strength and rigidity.
Preferably the grille system comprises three of four rod arrangements retained by each clamping member.
Each rod arrangement may comprise a straight rod wherein the second end portion is preferably also provided with an expanded portion.
Two pairs of straight rods may be provided with one pair arranged on a first straight line which is normal to a second straight line on which the other pair of rods is arranged, the first ends of each of the four rods are provided with expanded portions and received by a clamping member. A grille may be built up by providing the second ends of the rods with expanded portions for receipt by further clamping members.
The rod arrangement may comprise a cross or other lattice shape having at least a first end portion and a second end portion. Expanded portions may be provided on at least the first and second end portions.
The expanded portions are preferably integral with the rod arrangements. The expanded end portions are most preferably flared portions.
The rod arrangements may be of square or circular cross section and may be hollow or solid. The rods may be made from, for example, cold drawn steel, Electric Resistance Welded (ERW) steel tube or aluminium. The rod arrangements may be formed by upset forging or in the case of ERW steel tube swaging or pressing or in the case of aluminium die or sand casting.
The clamping member preferably comprises two separate but corresponding portions that can be joined together, for example by a bolt, to clamp the expanded ends of the rod arrangements therebetween. Each of the two separate portions comprises a central portion and a plurality of channel shaped limbs extending radially from the central portion to receive the ends of the rod arrangements. The channel shaped limbs of the clamping member are preferably canted away from the plane of the central portion of the clamping member in the direction in which the side walls of the channel shaped limbs extend. The channel shaped limbs are preferably canted at an angle of from 4xc2x0 to 5xc2x0 from the plane in which the central portion lies.
By way of their manufacturing tolerances the rod arrangements may vary in size. If the clamping device was rigid not all of the rods would be put under pressure. The use of a clamping device having a degree of cant and xe2x80x9cflexibilityxe2x80x9d results in all rod arrangements being gripped and the tolerance differential being overcome.
The clamping member is preferably cruciform in shape. The clamping member may be made from mild steel or spring steel. After heat treatment spring steel would provide more resilience to distortion and therefore a higher degree of security when used for security purposes.
The grille system of the present invention is particularly useful in the manufacture of a security grille whereby free ends of at least some of the rod arrangements are secured to a building so that the grille extends across a door or a window.
The grille system of the present invention can also be used in the manufacture of garden furniture and plant supports whereby decorative and load bearing structures are formed from the grille system.